From U.S. Pat. No. 3,263,258, a bristle cluster is know which is formed from bristles with differing diameters. By using bristles with differing diameters in a bristle cluster, the cleaning ability of the toothbrush should be improved because the thinner bristles can penetrate more easily into the interdental spaces, while the thicker bristles serve to clean dental regions that are easier to reach.
From both U.S. Pat. Nos. 5,313,909 and 4,802,255, toothbrushes are known in which the bristles of the toothbrush are made of what is known as “indicator filaments”. The indicator filaments have a colored region, wherein the use of the toothbrush leads to a change in the color of the colored region as the toothbrush continues to be used. The change in the color serves to indicate the wear on the toothbrush.